The field of the disclosure relates generally to a housing for a centrifugal fan, and more specifically, to methods and apparatus for uniform airflow distribution within a centrifugal fan.
Centrifugal fans or blowers are commonly used in the automotive, air handling and ventilation industries for directing large volumes of forced air, over a wide range of pressures, through a variety of air conditioning components. In a known centrifugal blower, air is drawn into a housing through one or more inlet openings by a rotating wheel. This air is then forced around the housing and out an outlet end. Known centrifugal blowers generate a high speed, non-uniform airflow that may produce undesirable whistling, tonal noise, or broadband noise as air travels through the blower housing. This noise may be caused by pressure changes within the airflow generated by portions of the airflow at different pressures interacting with each other or with a portion of the blower. The pressure variances in known blowers may be caused by turbulence in the airflow or airflow recirculation.
In at least some known centrifugal blowers, airflow recirculation may be caused by the mixing of an airflow entering the blower in an axial direction that is parallel to the axis of rotation of the blower wheel and the airflow within the blower that flows in a radial direction perpendicular to the same axis. Recirculating airflow generally has a swirling component that may generate undesirable flow structures, such as eddies or vortices, within the airflow. These vortices, in combination with the swirling recirculating flow, cause a non-uniform airflow within the blower housing and at the blower outlet that generates undesirable noise and facilitates inefficient operation of the centrifugal blower.
Moreover, as the airflow is exhausted from known blowers and enters a downstream conditioning component, it continues in the generally circumferential path it followed while inside the blower and tends to impact the sides of the downstream component, causing further undesirable noise and losses in the airflow. Additionally, the impact of the airflow on the component creates undesirable flow structures downstream of the blower that has an undesirable affect in upstream blower performance.